Electron discharge device



April 7, 1964 J. H. FlNK ELECTRON DISCHARGE DEVICE Filed Dec. 31, 1959 Fig unun... q.

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///l Il /Il /////////I/ It/Il INVENTOR Joel H.Fink.

ATTbRNEYB United States Patent 3,128,410 ELEtITRUN DESQHARGE DEVECE Joel H. Fink, Elmira, N.Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Fiied Dec. 31, 1959, Ser. No. 863,251 4 Claims. (61. 313-243) This invention relates to an electron discharge device and more particularly to an improved electrode assembly.

One particular application of this invention is in a rectifier tube used as a damper diode. A damper diode is a high perveance diode used in the horizontal deflection circuit of a television receiver. In this particular application, a tube is required to carry a relatively high current in the forward direction and also operate with a Very high peak inverse voltage. It is therefore desirable in order to maintain a low tube drop to locate the cathode and plate as close together as possible but the high peak inverse voltage limitation which sometimes may be as high as 5,000 volts requires that the cathode to anode close spacing be limited to avoid the possibility of arcing from the anode to the cathode.

The most important type of arcing which occurs in the damper diode occurs during the inverse part of the cycle when the anode is at a negative potential with respect to the cathode. In US. Patent No. 3,054,923 entitled Electron Discharge Tube, by B. Corson, issued September 18, 1962, and assigned to the same assignee, arcing problems associated with the support of the electrodes is discussed. During the time that the anode is negative with respect to the cathode, it is believed that there is field emission of electrons from the anode which are accelerated by the high voltage between the anode and cathode and strike the cathode. It is believed that this electron bombardment of the cathode causes the emission of gas from the cathode surface which may be in turn ionized by electron bombardment providing positive ions which in turn are accelerated to the anode and strike the anode causing a hot spot to appear. The heat from the positive ion bombardment will reduce the apparent work function of the anode material to permit further field emission of electrons. The electrons that are released from this hot spot will in turn be accelerated towards the positive cathode and acquires suficient energy to ionize more of the gas molecules within the space between the anode and cathode. Thus, another shower of positive ions is directed on the anode and this process results in very high inverse currents within the damper diode.

To minimize the probability of such an occurrence it is imperative that the gas content of such a tube should be as small as possible. Aside from the normal precautions taken in tube manufacture, the cathode must have been completely broken down during the exhaust process so that substantially no carbon dioxide may be released from the operating tube. In addition, any gas molecules such as oxygen released from the cathode during operation must be able to readily escape the region defined between the cathode and anode and be absorbed by a getter member positioned within the envelope.

It is accordingly an object of this invention to provide an electrode assembly which provides a low tube drop and yet obtains a substantial reduction in impedance to gas flow in the region defined between the cathode and anode. By reducing the impedance to gas flow within this region the processing of the tube is more thorough in that the carbon dioxide can be pumped out of the tube in a shorter time and it also permits more rapid dispersal of gase molecules such as oxygen released during the operating life of the tube.

It is accordingly another object to provide an improved high voltage tube.

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It is another object to provide an improved damper diode which will operate at high inverse voltages without arcing.

It is another object to provide electrode configuration in a diode to substantially reduce the impedance to gas flow between the cathode and anode.

These and other objects of this invention will be apparent from the following description taken in accordance with the accompanying drawings throughout which like reference characters indicate like parts, which drawings form a part of this application and in which:

FIGURE 1 shows an electron tube embodying this invention with the envelope and portions of the electrodes cut away to show the details of the electrode configuration;

FIG. 2 is an enlarged sectional view of the anode and cathode electrodes in FIG. 1 embodying the teaching of my invention; and

FIG. 3 is a sectional View of an anode and cathode assembly illustrating a prior art device.

Referring to FIGS. 1 and 2 there is shown a damper diode tube and more specifically tube type 6CQ4. The tube includes an evacuated envelope 11 of suitable material such as glass and having an electrode assembly positioned Within the envelope. The envelope 11 is comprised of an elongated tubular body portion 12 closed at one end and closed at the opposite end by a stem comprising a glass disk 14 to which is attached a base portion 16. The electrode assembly includes an anode 18, a cathode 30 and a cathode heater 32. In the embodiment shown, the cathode 30 is comprised of a cylindrical sleeve member 29 of an electrically conductive material, such as nickel, having a suitable electron emissive coating 31 such as barium and strontium oxide on its outer surface. The heater 32 is supported within the hollow part of the tubular sleeve 29 and is insulated therefrom by a spiral shield member 33. The heater 32 provides the necessary heat to cause electrons to be emitted from the electron emissive coating 31. The spiral shield member 33 is comprised of an electrically conductive coil coated with a ceramic insulating material. The anode 18 in one embodiment is of bi-part construction and consists of two identical metallic plate members 21 and 21. The plate members 21 and 21 may be formed to the desired shape by a pressing operation. The formed plate member 21 consists of two side flange portions 23 and 24 with semicylindrical outwardly oriented impression 22 positioned between the flanges 23 and 24 and an outwardly oriented step impression 25 connecting the edge of the semi-cylindrical impression 22 to the flanges 23 and 24. The flange 24 is provided with an outwardly oriented extension 26. The two plate members 21 and 21 are assembled together with their semi-tubular portions 22 and 22 facing outwardly and oppositely disposed. The two plates 21 and 21' are secured together by piercing the flange portions 23, 23, 24 and 24 in a plurality of points to form tab portions 27 at opposite ends of the opening 23 and the tabs 27 are then crimped on one side of the anode 18.

The interior region of the anode 18 as assembled comprises an elongated cylindrical region 15 defined by the semi-cylindrical portions 22 and 22' and two oppositely disposed radial channel regions 17 and 19 defined by the step portions 25 and 25'.

Support rods 36 and 38 are positioned within the channel regions 17 and 19 as formed by the step portions 25 and 25 and adjacent the flange portions 24 and 23 respectively. The rods 36 and 38 may be secured to the anode 18 by spot welding. The cathode 30 and anode 18 are assembled into an electrode assembly and retained there by means of a top support member 40 and a bottom support member 42 and top spacer member 44 and a bottom spacer member 46. The support members 40 and 42 may be made of any suitable rigid electrically insulating material such as glass. The members 40 and 42 are annular in shape having an interior aperture to provide clearance for the shield 33 and leads to the heater 32 and the cathode 30. The end portions of the anode support rods 36 and 38 are molded into the annular support members 40 and 42. The spacer members 44 and 46 are of a suitable material such as mica and in the form of a circular disk. The outer diameter of the disk is provided with serrated edges which bear against the inner surface of the envelope wall 14 and positions the electrode cage within the envelope.

The spacer members 44 and 46 have a central aperture therein which positions the sleeve 29 of the cathode. The support members 40 and 42 are secured to the spacer members 44 and 46 by oppositely disposed pins 50. A getter 52 is supported above the electrode cage by an extension of rod 38.

In FIG. 3, there is illustrated a prior art device which has a cathode 56 havin an outside diameter of 0.140 inch while the plate 58 has an inside diameter of .192 inch. In FIG. 2, the diameter of the cathode 30 is .140 inch and the outer diameter of the cylindrical region 15 is .192. The channels 17 and 19 are .040 inch by .142 inch. This increases the cross sectional area between the cathode and anode from .0135 square inch in FIG. 3 to .0232 square inch shown in FIG. 2. Out of a possible 360 of eflective anode area with minimum cathode to anode spacing approximately 48 has been lost due to the channels 1'7 and 19. This constitutes about 13% of the total and as a result the tube drop will be increased by less than 13%. The cross sectional area between the cathode and anode has almost double so the likelihood of arcing is substantially reduced.

While the present invention has been shown in only one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit and scope thereof.

What is claimed is:

1. A rectifier tube device comprising a cylindrical cathode and an anode, said anode comprising a first and a second sheet member, said sheet members comprising a semi-cylindrical portion, lateral portions extending outwardly from said cylindrical portion and fastening flange portions at the outer extremities of said lateral portions, said first and second sheet members fastened together at their flange portion to produce a cylindrical member into which said cylindrical cathode is inserted and spaced therefrom by about .052 inch, and oppositely disposed radial openings of about .040 inch between said lateral portions of said sheet member.

2. A rectifier tube comprising a tubular cathode and an anode surrounding said cathode, said anode comprising a pair of metal plates, each plate having a semitubular depression with flanges extending longitudinally thereof to define a hollow discharge space and equally spaced from said cathode by about .052 inch with oppositely disposed radial extending regions of about .142 inch in length communicating with said tubular discharge region defined by a portion of said flange adjacent said semitubular depression, said flanges spaced apart about .040 inch adjacent said semitubular depression.

3. A rectifier tube comprising an elongated cathode having a diameter of about .140 inch having a circular cross section and an anode, said anode comprised of a pair of metal plates, each plate having two side flanges and an elongated semicircular outwardly oriented impression and two side lateral impressions along the edge of said circular depression and between said flanges, said plates fastened together at their side flanges thereby producing an elongated substantially tubular member having an internal diameter of about .192 inch into which said cathode is inserted, and oppositely disposed elongated radial channels communicating with the region defined by said tubular member, said channels having a width of about .040 inch and extending for about .142 inch.

4. A rectifier device comprising an elongated cathode having a circular cross section of a diameter of about .140 inch and an anode, said anode defining an elongated circular region of about .192 inch inside diameter with radially oppositely disposed elongated communicating channel regions having a width of about .040 inch.

References Cited in the file of this patent UNITED STATES PATENTS 1,781,861 Rittenhouse Nov. 18, 1930 1,929,699 Loppacker Oct. 10, 1933 2,059,810 Rothe Nov. 3, 1936 2,301,012 Briggs Nov. 3, 1942 2,372,379 Ishler Mar. 27, 1945 2,448,559 Stutsman Sept. 7, 1948 2,589,397 Koehler Mar. 18, 1952 

1. A RECTIFIER TUBE DEVICE COMPRISING A CYLINDRICAL CATHODE AND AN ANODE, SAID ANODE COMPRISING A FIRST AND A SECOND SHEET MEMBER, SAID SHEET MEMBERS COMPRISING A SEMI-CYLINDRICAL PORTION, LATERAL PORTIONS EXTENDING OUTWARDLY FROM SAID CYLINDRICAL PORTION AND FASTENING FLANGE PORTIONS AT THE OUTER EXTREMITIES OF SAID LATERAL PORTIONS SAID FIRST AND SECOND SHEET MEMBERS FASTENED TOGETHER AT THEIR FLANGE PORTION TO PRODUCE A CYLINDRICAL MEMBER INTO WHICH SAID CYLINDRICAL CATHODE IS INSERTED AND SPACED THEREFROM BY ABOUT .052 INCH, AND OPPOSITELY DISPOSED RADIAL OPENINGS OF ABOUT .040 INCH BETWEEN SAID LATERAL PORTIONS OF SAID SHEET MEMBER. 